Effect of Different Coatings on Friction and Wear of Cemented Carbide and Micro-Drilling Performance

Cemented carbide micro-drills are essential tools in printed circuit board (PCB) manufacturing, and surface coatings are a critical factor influencing their service performance. This study investigated the effects of CrAlN and TiCrAlN coatings on the friction and wear characteristics of WC–8.5Co cemented carbide as well as the drilling performance of micro-drills.Overall, the results demonstrate that the wear resistance of the investigated materials follows the order: TiCrAlN-coated alloy > CrAlN-coated alloy > uncoated alloy. Specifically, in the tribological tests, the TiCrAlN-coated alloy, owing to its higher hardness and elastic modulus, exhibited a reduced volumetric wear rate from 3.4 × 10?? mm3·N?1·m?1 for the uncoated alloy to approximately 2.1 × 10?? mm3·N?1·m?1, indicating that the coating significantly improves the wear resistance of the alloy. In the drilling tests, severe abrasive wear occurred on the flank face of the uncoated micro-drills due to the adhesion of high-hardness oxides such as SiO?. In contrast, the dominant adhered species on the flank face of the coated micro-drills shifted to Cu with relatively lower hardness, resulting in a reduced degree of tool wear. The transformation of adhesive materials is attributed to the increased surface hardness, denser structure, and improved chemical stability of the micro drill surface after coating deposition, which prevents fillers such as SiO? in the PCB substrate from becoming embedded. After drilling 10,000 holes, the flank face of the uncoated micro-drills was completely worn, whereas the TiCrAlN-coated micro-drills retained a relatively intact cutting edge, with a flank wear ratio of approximately 30%, demonstrating enhanced wear and adhesion resistance and highlighting its effectiveness in improving drilling performance.